AbstractBackgroundWork‐life conflict (WLC) has a critical effect on employee mental health. However, research on occupational health has neglected the family domain. Furthermore, although it is reasonable to assume that the effect of WLC on health may differ according to socioeconomic circumstances, there is little empirical evidence for differences in the impact of WLC by socioeconomic status (SES). The purpose of this study was to assess the role of SES as an effect modifier, while examining whether the SES level affects the relationship between WLC and mental health.MethodWe analyzed data from the nationally representative South Korean Working Conditions Survey of 2014, including 49 401 workers. Logistic regression analyses, stratified by sexes, were performed to identify sex differences, and interaction terms including WLC and SES were also incorporated.ResultsWLC (men: OR = 1.24; women: OR = 1.18) and domestic demands (men: OR = 1.16; women: OR = 1.22) were significantly associated with mental health. WLC exhibited a stronger association with mental health for individuals with high SES, both in terms of education (men: OR = 1.61 vs 1.51; women: OR = 1.52 vs 1.24) and income (men: OR = 1.44 vs 1.10; women: OR = 1.48 vs 1.20).ConclusionsOur data suggest that future efforts for health promotion should consider workers’ family demands and SES as important modifying factors of psychological health in the workplace.